Abstract:In this study, the influence of various factors on nitrogen oxides (NOx) emissions of a low NOx burner is investigated using a central composite design (CCD) approach to an experimental matrix in order to show the applicability of design of experiments methodology to the combustion field. Four factors have been analyzed in terms of their impact on NOx formation: hydrogen fraction in the fuel (0%-15% mass fraction in hydrogen-enriched methane), amount of excess air (5%-30%), burner head position (20-25 mm from the burner throat) and secondary fuel fraction provided to the burner (0%-6%). The measurements were performed at a constant thermal load equal to 25 kW (calculated based on lower heating value). Response surface methodology and CCD were used to develop a second-degree polynomial regression model of the burner NOx emissions. The significance of the tested factors over their respective ranges has been evaluated using the analysis of variance and by the consideration of the coefficients of the model equation. Results show that hydrogen addition to methane leads to increased NOx emissions in comparison to emissions from pure methane combustion. Hydrogen content in a fuel is the strongest factor affecting NOx emissions among all the factors tested. Lower NOx formation because of increased excess air was observed when the burner was fuelled by pure methane, but this effect diminished for hydrogen-rich fuel mixtures. NOx emissions were slightly reduced when the burner head was shifted closer to the burner outer tube, whereas a OPEN ACCESSEnergies 2015, 8 3607 secondary fuel stream provided to the burner was found to have no impact on NOx emissions over the investigated range of factors.
Available online xxxKeywords: Low-NO x burner Bluff body flow Nitrogen oxides Particle imaging velocimetry a b s t r a c t The increased need for fuel flexibility and CO 2 capture solutions (CCS) in the power and industrial sectors has led to higher focus on hydrogen containing fuels. The high reactivity and combustion temperature in hydrogen flames are a source of high nitrogen oxides (NO x ) and a barrier to the implementation of traditional dry lean premixed low NOx burner technology. The present experimental study investigates emissions of NOx and characterises the turbulent flow field above a promising burner concept based on partially premixed bluff body (PPBB) strategy. The PPBB burner configuration allows for a rapid mixing of fuel and air through multiple fuel injection in the accelerating air stream, followed by a flame stabilization process controlled by a bluff body. The measurements were conducted using methane, hydrogen, and a methaneehydrogen mixture 50/50 mass fraction as fuels and at various burner thermal loads ranging from 10 kW to 25 kW. The turbulent flow field characterisation was made by Particle Image Velocimetry (PIV) without the combustion chamber and in selected operation modes. Several burner parameters were varied, as the position of the bluff body and the fuel distribution. Shifting the burner lance controlling the bluff body position to accelerate the air flow resulted in lower NO x emissions, although negatively affecting the flame stability and generating incomplete combustion. Supplying fuel through secondary fuel ports had opposite effect on NO x emissions depending on the fuel: an increase for methane and a decrease for hydrogen. The temperature of the chamber has significant impact on NO x emissions and was quantified in the study with a 50% increase from a chamber temperature of 700 Ce1050 C. NO x emissions are generally higher as the hydrogen content in the fuel increases. The lowest achieved NO x emissions are 26 and 66 ppm at 3% O 2 dry for methane and hydrogen respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.